Amino acids are compounds constituting a basic unit of protein, and an α-amino acid is an amino acid in which an amino group and a carboxy group are bonded to the same carbon. In general, the α-amino acid is frequently referred to simply as an amino acid.
The α-amino acid is in great demand for intermediates of a variety of industrial chemicals and also food additives, nutritional supplements, feed additives, medicaments, etc.
As its production method, in addition to a method of hydrolyzing a natural protein, a chemical synthesis method, a fermentation method, and an enzymatic method are adopted. Among these, as the chemical synthesis method, so-called hydantoin method and Strecker method, and so on are widely known.
The hydantoin method is a method in which an aldehyde or ketone compound is allowed to react with hydrogen cyanide and ammonium carbonate to synthesize hydantoin, which is then subjected to alkaline hydrolysis to obtain an α-amino acid. In the hydantoin method, in order to obtain an α-amino acid, after the alkaline hydrolysis, it is necessary to repeat a separation step of α-amino acid crystallized through neutralization with an acid, and a desalting step for removing a salt formed through neutralization is also needed, and thus, there was such a problem that the number of steps becomes large.
Meanwhile, the Strecker method is a method in which an aldehyde or ketone compound is allowed to react with hydrogen cyanide and ammonia to synthesize an α-aminonitrile, which is then hydrolyzed to obtain an α-amino acid. In the Strecker method, conventionally, the hydrolysis of the α-aminonitrile was also executed with an alkali, and similar to the aforementioned hydantoin method, neutralization with an acid was needed, and a desalting step for removing the thus formed salt was needed.
A technology for producing an α-amino acid capable of simplifying such complicated steps is demanded.
For example, PTL 1 describes a method for producing an α-amino acid, including bringing an α-amino acid amide into contact with water in a liquid phase in the presence of at least one metal oxide selected from the group consisting of zirconium oxide, titanium oxide, and niobium oxide, thereby performing hydrolysis.
In addition, PTL 2 describes a method for producing an α-amino acid, including bringing an α-amino acid amide into contact with water in a liquid phase in the presence of a complex metal oxide.